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Old 07-28-2008, 08:52 PM   #1
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500 Ft Of Wire To My Barn


I Want To Run 500 Ft Of Wire From The Panel At My House Underground To My Barn. for lights only.......whats The Smallest Gauge Wire
I Can Get Away With - Also What Size Breaker At The Panel
- Total Light Wattage 450w - no other power required


Last edited by IGNATZ; 07-28-2008 at 08:55 PM.
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Old 07-28-2008, 09:15 PM   #2
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500 Ft Of Wire To My Barn


According to my electric calc program to get a 15 amp supply at the barn, and stay below the recomended 3% voltage drop, you will need to run 4awg copper minimum.

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Old 07-28-2008, 09:28 PM   #3
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500 Ft Of Wire To My Barn


dont need 15 amps at the barn just enough to lite up 450 watts
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Old 07-28-2008, 09:30 PM   #4
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500 Ft Of Wire To My Barn


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Originally Posted by IGNATZ View Post
I Want To Run 500 Ft Of Wire From The Panel At My House Underground To My Barn. for lights only.......whats The Smallest Gauge Wire
I Can Get Away With - Also What Size Breaker At The Panel
- Total Light Wattage 450w - no other power required
And running the lights on 12v means shipping 37a over 500'; not good.

If the load is only on intermittently you could do a battery arrangement and just run the low charging current over the 500' at low voltage.
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Old 07-28-2008, 10:41 PM   #5
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500 Ft Of Wire To My Barn


# 8 AWG copper would be the smallest you could go, and it would be fed by a 15 amp breaker.


What I would do though is pull a multiwire branch circuit out to the barn, that means two hots, a neutral and a ground, and split the load up evenly, and then you could probably get away with running # 10 AWG out to the barn.

Last edited by chris75; 07-28-2008 at 10:46 PM.
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Old 07-29-2008, 10:41 PM   #6
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500 Ft Of Wire To My Barn


voltage drop

vd=2KID/circular mils
2xK (constant, 12.9 for copper) xI(amps) xD(distance)

so 450w. at 120v is 3.75 amps. and the distance is 500 feet.

2x12.9x3.75x500=48375

now divide that by the size of the wire in circular mils (this is where the codebook comes in handy) for #14 its 4110, for #12 its 6530, #10 is 10380.

for #14, you would get almost a 12v. drop. your only allowed 3% of 120 (3.6volts).
#12 gets you 7.4 drop
#10 gets you 4.6 drop.
if i were you, and your only running a couple of lights, and you want to save money, use the #12, 120 volts, 110 volts, its the same thing, so why not 112.6? your lights will still work.
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Old 07-30-2008, 06:21 AM   #7
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500 Ft Of Wire To My Barn


If I was going to dig a ditch 500 ft. long (lot of work) I would at least put a least a 10/3 wG UF cable in the hole! (#10 seems to be the most bang for the buck)
Put a very small subpanel in the barn with two 120 circuits. One for the lights and at least one outlet.(GFIC on both)
Never know when you will want to plug something in!

You won't be doing any welding out there but you will have plently of light.
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Old 07-30-2008, 02:12 PM   #8
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500 Ft Of Wire To My Barn


I agree with napper. Trenching 500' is long way to go for such a small amount of capability. Go bigger, you will not be sorry. Your wallet will be considerably lighter though.
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Old 07-30-2008, 03:11 PM   #9
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500 Ft Of Wire To My Barn


I would consider a solar charger, battery, inverter, and light. Should be cheaper than the cost of trenching. Last trench cost me $200, for 85'.
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Old 07-30-2008, 03:32 PM   #10
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500 Ft Of Wire To My Barn


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I would consider a solar charger, battery, inverter, and light. Should be cheaper than the cost of trenching. Last trench cost me $200, for 85'.
or a 2/3 hp gasoline engine and an alternator/generator. Probably some hobby engines can put out this much power.
At one or two kilobucks for the 15A job, for the same or less money you can probably get a pretty good setup that's "off the grid."

A square solar array for this much continuous power would be ~9' on a side. If the lights are on 1/3rd of the time, ~5' on a side.

Speaking of shipping power over a 500' distance and not wanting to trench, I e-mailed the NFPA to ask if there is some voltage or current or power below which the NEC doesn't care.
They haven't answered yet.

A good guess is something less than 30vrms, less than 42v peak, less than 60vdc, and above 12vrms.
I think workers in underground sewers, standing in water, use 24v or 28v for the lighting.

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Old 07-30-2008, 03:52 PM   #11
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500 Ft Of Wire To My Barn


jb fan, wish I could charge that much for a trench here. When i tell somebody $1.00 per foot or $100.00 minimum they act like I asked for their first born child! Needless to say most of my trenching is for my own needs.
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Old 07-30-2008, 06:35 PM   #12
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500 Ft Of Wire To My Barn


Here at the 208xx zip code area, a 36" walk-behind trencher is ~$170/day.
I'd think 5 hours would do 500' on flat ground, no stones, no roots.
http://www.sunbeltrentals.com/equipm...FQiNHgodWlNaSg

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Old 07-30-2008, 07:19 PM   #13
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500 Ft Of Wire To My Barn


No way would I trench 500' just to direct bury UF. It would probably be 1.25" pvc minimum if I'm going to take the time to run power to a shed.

Burying UF will likely result in one of these two callbacks:

"I think I have a break in the wire cause I lost power to my shed."

"I added a couple more things to my shed but now the breaker trips? What can we do to fix it?"
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Old 07-30-2008, 07:21 PM   #14
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500 Ft Of Wire To My Barn


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Originally Posted by Cow View Post
No way would I trench 500' just to direct bury UF. It would probably be 1.25" pvc minimum if I'm going to take the time to run power to a shed.

Burying UF will likely result in one of these two callbacks:

"I think I have a break in the wire cause I lost power to my shed."

"I added a couple more things to my shed but now the breaker trips? What can we do to fix it?"

How bout this one, I think we sized the voltage drop wrong, my light is very very dim...
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Old 07-30-2008, 09:11 PM   #15
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500 Ft Of Wire To My Barn


Quote:
Originally Posted by Cow View Post
No way would I trench 500' just to direct bury UF. It would probably be 1.25" pvc minimum if I'm going to take the time to run power to a shed.

Burying UF will likely result in one of these two callbacks:

"I think I have a break in the wire cause I lost power to my shed."

"I added a couple more things to my shed but now the breaker trips? What can we do to fix it?"
Agreed. For less than $175 in conduit, it would be much better to have the ability to upgrade later. Plus, the cost of THWN (plus the conduit) vs. UF, the total would probably come out the same.


Last edited by jerryh3; 07-30-2008 at 09:13 PM.
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